So can I get the (remote ?) HDD's/directories to show up like an external drive or a regular old HDD partition ?
(via a GUI). How would I achieve that ?

When I use network manager on my machines, they each see the SSID of the router.
Do I need to get the IP address of the machine that I want to connect to and then try to connect that way ?
Using what programme ?

Also, I had read (in an old LXF special) that NFS wasn't the best solution nower-days as it's insecure ??
Which seems a shame, as it looks like a good solution.